Diaphragms and Caps

Diaphragms and caps are barrier methods of contraception. They are convenient, but not quite as reliable as various other methods of contraception.

What are diaphragms and caps?

  • Diaphragms are dome-shaped devices. They are usually made from soft rubber or silicone. They are put into the vagina and form a barrier between sperm and the womb. There are various different types and sizes.
  • Caps are smaller and firmer than diaphragms. They cover just the cervix. They are used much less often than diaphragms. They may be used by women who are troubled with cystitis (bladder infection) when using a diaphragm.

You should also use a spermicide each time you use a diaphragm or cap. Spermicide kills sperm.

How effective are diaphragms and caps?

About 20 women in 1000 will become pregnant each year when barrier methods are used perfectly for contraception. Nearer to 160 women in 1000 will become pregnant with normal (not perfect) usage. When no contraception is used, more than 800 out of 1000 sexually active women become pregnant within one year.

Other methods of contraception are more reliable than this. Several other methods of contraception are more than 99% effective. However, some women prefer to use a diaphragm or cap.

What are the advantages of diaphragms and caps?

They are easy use and do not have any serious medical risks. You only have to use them when you have sex. The advantage over a male condom is that you can put it into the vagina at any time before sex.

What are the disadvantages of diaphragms and caps?

You have to learn how to use them properly. Some women get bladder infections after using a diaphragm. The spermicide and rubber may be messy and may irritate you.

There is little evidence that they can protect against sexually transmitted infections or HIV infection. Women who have HIV or AIDS (or who are at high risk of HIV infection) are not usually recommended to use a diaphragm or cap.

How are diaphragms and caps used?

A doctor or nurse will examine you and advise on the correct size and shape that would suit you. They will show you how to put in and take out the diaphragm or cap. They will also show you how to use the spermicide. This must be used every time you use the diaphragm or cap. You need to be confident that you can put it in correctly over your cervix, know how much spermicide to use and how to use it.

You are likely to be given a 'practice' diaphragm or cap by the doctor or nurse. This is for you to practise at home putting it in and out. This is not to be used for contraception. At a follow-up appointment the doctor or nurse will check that everything is fine, and then give you a real one for contraceptive use.

Some useful points about diaphragms and caps:

  • You can insert a diaphragm or cap at any time before sex. However, you need to use extra spermicide if you have sex more than three hours after you put it in.
  • It must be left in place for at least six hours after last having sex.
  • Use extra spermicide if you have sex again before taking it out.
  • Do not leave it in for more than 30 hours in total. This is to prevent the possibility of toxic shock syndrome. This is a very rare but serious type of blood poisoning caused by toxin-producing bacteria.
  • Do not use them during your period.
  • Don't have a bath with the diaphragm or cap in place. The water may wash away the spermicide or move the cap out of position. Showers are fine.

Who should not use diaphragms or caps?

They should not be used:

  • If the muscles in your vagina are not firm enough to hold the diaphragm or cap in place.
  • If you have an unusual shape or position of your cervix. The doctor or nurse will advise about this when they examine you for correct fitting.
  • If you are allergic or sensitive to rubber or spermicide.
  • If you have repeated urine infections, it may not be advisable.
  • If you have ever had toxic shock syndrome.

Looking after a rubber diaphragm and cap

  • Wash it with warm water and mild soap after use. Rinse with lots of water.
  • Dry gently and keep it in the box provided.
  • Never use detergents, boiling water, disinfectants, etc, which can damage the rubber.
  • Check it for damage, tears, etc, before using. Hold it up to the light to check there are no holes.
  • Depending on how often it is used, it may need replacing every year or so.

Some other points about diaphragms and caps

  • Size - you may need a different size if you gain or lose more than 3 kg in weight, or have a baby. A doctor or nurse will need to examine you to re-assess your size.
  • Lubricants - don't use oil-based products such as Vaseline®, body oils, lotions, etc, during sex. They can damage rubber. If you want to use a lubricant then use K-Y Jelly® or extra spermicide.
  • Infection - don't use it if you have a vaginal infection such as thrush. Wait until the infection clears.

You doctor or nurse may give you a prescription for emergency contraception to have in advance. This can be useful - for example, if you were to take the diaphragm out earlier than six hours after having sex.

See separate leaflet called Emergency Contraception for further detail.